This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The use of dental amalgam as a direct restoration material has been controversial for several decades because of potential health hazards caused by leeching of metals and in particular of mercury. Some mercury forms (such as methylmercury species) are considerably more toxic than others (such as the elemental form). Thus, in order to help assess the potential hazards of dental amalgam, it is necessary to establish not only how much of a given element is leeched under various conditions, but also the element?s chemical form. In this proposed research, we plan to apply X-ray absorption spectroscopy (XAS) to study what chemical species may be released from dental amalgam of different ages under various treatments mimicking normal oral exposures such as pristine saliva, food and drink, toothpaste and mouthwash. Information obtained from this study will assist in understanding released metal toxicological behavior at the molecular scale, and will provide much-needed insights into the potential hazards or otherwise of the use of dental amalgam.